Short communication: Teat skin pH.

Changes in teat skin surface pH were studied over 12 wk in 99 lactating Holstein cows. Half the udder of each cow routinely received postmilking disinfection, and the other half served as control. Measures of pH were made on all teats at weekly intervals. Teat skin pH was affected by treatment but not week. Mean teat skin pH measures were: 7.18 (+/- 0.64) and 7.53 (+/- 0.46) for treatment and control teats. In study II, pH teat skin measures were made hourly on 16 cows, starting 2 h before milking, immediately before a milking, immediately after a milking, and for 2 h postmilking. Teat skin pH was significantly lower for treatment teats and was lower for all teats postmilking.

Efficacy of two acidified chlorite postmilking teat disinfectants with sodium dodecylbenzene sulfonic acid on prevention of contagious mastitis using an experimental challenge protocol.

Two acidified sodium chlorite postmilking teat disinfectants were evaluated for efficacy against Staphylococcus aureus and Streptococcus agalactiae by using National Mastitis Council experimental challenge procedures. The effect of these teat dips on teat skin and teat end condition was also determined. Both dips contained 0.32% sodium chlorite, 1.32% lactic, and 2.5% glycerin. Dips differed in the amount of sodium dodecylbenzene sulfonic acid (0.53 or 0.27%) added as a surfactant. Both dips significantly reduced new intramammary infection (IMI) rates compared with undipped controls. The dip containing 0.53% dodecylbenzene sulfonic acid reduced new IMI by Staph. aureus by 72% and Strep. agalactiae by 75%. The dip containing 0.27% dodecylbenzene sulfonic acid reduced new IMI by Staph. aureus by 100% and by Strep. agalactiae by 88%. Changes in teat skin and teat end condition for treatment and control groups varied in parallel over time. Teats treated with either teat dip had higher mean teat skin and teat end scores than control teats at some weeks. However, teat skin and teat end condition did not tend to change from the start to the completion of the trial. Application of the two new postmilking teat dips was effective in reducing new IMI from contagious mastitis pathogens. (Key words: teat dip, contagious mastitis, chlorous acid)